Messier Sweep is a planner and logbook for the Messier marathon that runs entirely on your device. It has no account, no sign-in and no servers of its own. This page explains exactly what the app touches and where it stays.
None. Messier Sweep does not collect, transmit or receive any personal data, usage data, analytics or identifiers. There is no backend for the app's features, no advertising, no tracking, and no third‑party SDKs of any kind embedded in the app.
Everything the app remembers is written to your device's local storage and never leaves it:
If you tap "Use my location" in the planner, the app reads your location once, on demand, to fill in a latitude and time zone for its offline sunrise/sunset and twilight calculations. That rounded value is stored only on your device and is never transmitted anywhere. You can also type a latitude by hand and skip location entirely.
The app can attach a picture to a sighting using your camera or the system photo picker. These are used only when you choose to add a photo to a sighting, and the image is copied into the app's own on‑device storage. The app never scans your photo library and never uploads a photo anywhere.
If you turn on night alerts for a planned marathon, the app schedules local notifications on your device (an afternoon reminder, one before astronomical dusk and one before dawn). These are generated and delivered entirely on your device — no push service or remote server is involved.
Messier Sweep does not share data with anyone because it does not collect any. There are no third‑party analytics, advertising or crash‑reporting libraries in the app. When you use the system share sheet to export a marathon summary, that action is entirely under your control and goes wherever you choose to send it — the app itself is not a party to it.
Messier Sweep does not knowingly collect information from anyone, including children, because it does not collect information at all.
You can erase everything the app has stored at any time from Settings → Erase all data. Deleting the app also removes all of its local data from your device.
If this policy changes, the "last updated" date above will change with it. Continued use of the app after an update means you accept the revised policy.
Questions about this policy can be sent through the contact form on our support page.